The specific aim of this project is to characterize the etiology and pathogenesis of progressive post infarction mitral insufficiency. Through this characterization, the following hypothesis will be tested: The left ventricle undergoes global remodeling following posterior wall myocardial infarction. This remodeling occurs in a distinct pattern and is a result of alteration in regional wall stresses which results in progressive post infarction mitral insufficiency. A recently described large animal model of progressive ischemic mitral insufficiency will be used to collect serial sets of data. An array of 37 miniature radiopaque markers will be placed throughout the left ventricle, mitral annulus, leaflets, and papillary muscles. The simultaneous 3-D location of these markers will then be followed throughout all phases of the cardiac cycle using high-speed, biplane radiographic images each 16.7 msec. Data will be collected four times over a twelve week period permitting the evaluation and tracking of changes in all components of the mitral valve as post infarction mitral insufficiency develops. Histologic analysis of the remodeling left ventricle will also be performed to correlate ultrastructural evolution with changes in the biomechanical environment. This novel approach of evaluating both biomechanical and ultrastructural changes may be necessary to definitively elucidate the basic cardiovascular mechanism of this perplexing clinical problem.